Michael Smith celebrates the Browns' stockpiling draft picks, getting a second-rounder in 2018 in addition to Brock Osweiler from the Texans. (1:04)

Many of us are still geeking out about Thursday's unusual trade between the Houston Texans and Cleveland Browns, mostly because few ever conceived of the possibility. Who ever thought that one NFL team could use draft choices to entice another to take on a terrible contract?

2017 NFL Free Agency

• Latest free-agent signings, reaction

• Barnwell's free agency grades

• Seifert's winners, losers from Day 1

• Graziano's biggest surprises from Day 1

• Schefter's latest updates

• Fantasy analysis of free-agent signings

• NFL players react to Day 1 moves

• Top 150 free agents

(ESPN colleague Bill Barnwell did, in December, but apparently no one noticed -- except perhaps the Texans and Browns.)

That's essentially what happened Thursday, when the Texans sent quarterback Brock Osweiler (and his $16 million salary-cap hit) and two draft picks to the Browns in exchange for one draft pick. The Browns continued their strategy of stockpiling picks, while the Texans rid themselves of Osweiler and his contract.

The deal was perfectly legal, but its unprecedented nature makes it worth a review of the NFL's trade policies and procedures. So while we have a moment on this glorious Friday, let's do just that.

Why was there any question about this trade's legality?

The NFL doesn't want teams purchasing assets in trades. In a worst-case scenario, it would spur free-spending owners to buy up players, draft picks and cap space without giving anything but money in return. That approach would counter the league's revenue-sharing and equalizing conceit. The policy states: "Any trade of a draft choice or draft choices, or of player contract rights or negotiation rights, for any amount of money, is conduct detrimental to the league."

Is that what happened here?

No. Cap space exchanged hands, but no cash. Osweiler's $16 million hit shifted from the Texans to the Browns -- but that happens whenever a player is traded. The Browns might not have plans for Osweiler and could part ways with him long before they begin offseason workouts, but that doesn't violate any rules.

Would this trade have been announced if there was any question about its legality?

Almost certainly not. All proposed trades, other than those that occur on draft day, must be submitted in writing to commissioner Roger Goodell's office. The policy states the trade won't be accepted if the submission is incomplete, incorrect or not in compliance with league rules or the collective bargaining agreement.

Sometimes rumors of a trade leak out before league approval, but both teams announced this one Thursday afternoon. Publicizing it in an official way before league approval would have risked scuttling it entirely.

The Texans sent quarterback Brock Osweiler (and his $16 million salary-cap hit) and two draft picks to the Browns in exchange for one draft pick. Leslie Plaza Johnson/Icon Sportswire

Other than using cash, are there any other restrictions to NFL trades?

The policy features this guiding statement: "There shall be no trades for past, future or nominal consideration."

In this case, nominal likely means "far below the real value or cost." We could go down a deep rabbit hole on how real value is determined. Suffice it to say, an NFL team could not trade a 2017 first-round pick for a 2017 fifth-round pick, if it ever were so inclined.

What would "past" or "future" consideration mean?

This is a way to ensure that all trades are self-contained. A deal can't be lopsided to correct a previous inequality, nor could a trade be made that would include future compensation to be determined.

Don't teams make "contingent" trades all the time?

Yes, but the terms are always spelled out in advance. For example, a team could receive a fifth-round pick if a player plays at least 50 percent of his new team's snaps or a fourth-round pick if he starts 80 percent or more. The contingencies are all accounted for.

Any other rules to know?

Trades can't include a condition that would revert the player back to his original team after a specified period of time. In other words, one team can't overtly "loan" a player to another. The player can't return to the original team until two seasons have elapsed, unless he meets a series of exceptions that includes being waived after a minimum of four games on the roster.