Should the negotiations here stall, and the players choose to decertify as a union, ownership would almost certainly declare their intentions to lock out the players. Then the players likely would move to get relief from U.S. District Judge David S. Doty in the form of an injunction. It's not certain what Doty would do, of course, but he has made some significant pro-player decisions while overseeing NFL labor. If Doty granted injunctive relief, he could likely rule that the league's last work rules were still applicable, or he could simply allow the NFL to institute a set of rules of its choosing. But it's a virtual certainty the NFL would appeal the injunction.
If the injunction survived the appeal process, the 2011 league year would start and the rules would include free agency and the ability to trade players.