It was the first good beach day of the season at Brighton this Saturday and I was doing everything right.

I found a good spot close to the water. I remembered to put a towel in my bag. My buddy had a sun tent we were trying out for the summer. And, like plenty of beachgoers from Ocean Avenue all the way down to MCU Park, I was nursing a beer.

There too, I was doing it right: I kept the bottle in a paper bag, hidden under my towel. I waved off the potent “nutcrackers” that hawkers were selling because it wasn’t yet 2 p.m. But in the eyes of the law, of course, none of that matters.

You know the end of this story. Two NYPD officers in shorts pulled up behind me in a golf cart contraption and came over to chat — and to issue a summons for drinking from an open container.

My first criminal summons came just days before a 2016 law came into effect, making the classic NYC offense a mere civil violation. That happened on Tuesday when the NYPD unveiled rules mandated by the legislation that give officers the option to issue a civil penalty for offenses like public urination, littering, and of course enjoying a cold one in the great outdoors.

Saturday’s fun and games were a good accidental example of the positives of the new policy, and also its limitations.

Notes from the waning days of the old system

First, the cops asked where I was from. I wanted to say, “Brooklyn, where we’ve been drinking responsibly, more or less, for decades.” Instead I just said, “Brooklyn.” Then they asked whether they could see some ID.

That’s potential problem number one, which unfortunately is true in both the new and old systems. I had ID on me, but if I didn’t, they would have taken me down to the precinct and the encounter would have escalated beyond a simple summons.

Then for about 10 minutes they ran my ID to see whether I had any warrants or open investigations, which naturally would have meant handcuffs.

Ultimately their software discovered that I was not public enemy No. 1, and one of the officers wrote out the ticket. For years, New Yorkers have had the pleasant ability to “plea by mail” for public consumption of alcohol — that is, plead guilty and pay your $25 without showing up to court. The cops urged me to do so and said have a nice day.

That thin pink slip of paper probably deserved a little more attention, and it’s the main reform addressed in the new system. Since the paper constituted a criminal summons, if I lost it on the way home and didn’t show up at court, there would be a warrant out for my arrest. If I forgot to pay the money within 10 days: warrant. Then if I ever got stopped for another outdoor beer, the warrant would mean time locked-up, a somewhat cyclical scenario. For New Yorkers who aren’t citizens, such a turn of events could have much more serious implications.

Concerned about the possibilities, I filled out the form, wrote a check and put both in the mail on Monday, nervously ignoring a tweet I saw from an NYPD precinct warning residents about the possibility of “mailbox fishing,” in which people take checks out of mailboxes.

Criminal justice reform, little by little

Then, Tuesday, the big day of change. For drinking in public, excessive noise, littering, spitting, urinating in public, and violating parks rules, cops are now directed in many cases to write out a civil summons, like a ticket. This has been the crowning criminal justice reform for outgoing City Council Speaker Melissa Mark-Viverito, potentially diverting tens of thousands from the criminal justice system. Through the civil process, there are no warrants if you forget to pay the first ticket, and you can pay that ticket online.

Some critics are already decrying the new policy as the end to law and order, but there are leftist detractors, too, given the ease with which cops can still use criminal summonses or arrests: if someone has an open warrant, is on parole or probation, has been arrested for two or more felonies over two years, or if they have three unanswered civil summonses. All of those could limit the effectiveness of the City Council’s reforms, depending on what the NYPD does.

My summons and check safely in the mail (I hope), I called Bob Gangi, a longtime criminal justice reform advocate now running an uphill primary battle for mayor.

“You?” he laughed. “I’m glad to see they nailed a probably respectable looking white guy.” Gangi has long pointed to the racial disparities in who gets arrested or stopped by police in NYC, with far more serious repercussions than a $25 fine.

One common argument for why low-level offenses need to be on the books is so cops can use them for people who are indeed making trouble. But Gangi says there are specific statutes for that — disorderly conduct or reckless endangerment, for example, both of which are already broad and rely on NYPD discretion.

To be fair, the officers who gave me my summons were nice enough about it, not being aggressive or dinging me for a more expensive glass-bottle violation. (Heineken, sorry). But at the end of the day you may have to scratch your head and wonder whether a simple beer on the beach is a pressing problem of morality or crime, criminal or civil, given the boardwalk bars a few hundred feet away and the need for police resources on more serious issues.

That’s the $25 question.