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Several years ago, the NFL acknowledged the rampant pre-free agency tampering by creating a window for permissible pre-free agency tampering. Meanwhile, impermissible pre-free agency tampering continues, largely unchecked.

Each year, the league office sends out a memo containing a list of do’s and don’ts. The 2017 memo was distributed to all teams today.

The permissible pre-free agency tampering window opens at 12:00 p.m. ET on Tuesday, and it lasts until “3:59:59 p.m.” ET on Thursday. During that window, teams may enter into contract negotiations with agents representing the players who will become free agents at 4:00 p.m. ET on Thursday.

“During the two-day negotiating period, all clubs may negotiate all aspects of an NFL Player Contract with the certified agent of any prospective UFA,” the memo explains. “However, a new club may not execute an NFL Player Contract with a prospective UFA until 4:00 p.m., New York time, on March 9, when the player’s 2016 contract expires.”

Prohibited actions during the legal tampering window include: (1) executing a player contract; (2) executing an agreement in principle “or similar document”; (3) announcing that an agreement in principle or similar agreement has been reached; (4) violating the CBA provisions that relate to undisclosed contractual terms. (That last one presumably applies even after free agency officially begins.)

Reading between the lines, a verbal agreement in principle is permitted, as long as it’s not announced. Inevitably, agreements in principle will be reached and leaked. Still, no deal is done until it is signed, and no deal can be signed until after 4:00 p.m. ET on Thursday.

Teams also cannot make travel arrangements for player visits, and there can be no communication with the player — even if he represents himself. This means that the rest of the tackle market will get even more of a head start on Russell Okung, especially after the illegal tampering that happened at the Scouting Combine. (At one point, there was a belief that Okung would show up in Indianapolis with the goal of negotiating a contract.)

Even though free agency doesn’t really open until Thursday, it actually opens on Tuesday. And plenty of unofficial deals will be done, quickly.