The league can and will suspend players without charges under personal conduct policy (and has plenty of times before). In fact the policy specifies that it doesn't require charges or a conviction to result in a suspension. Just in recent memory, Zeke Elliott got 6 games (never charged, appealed suspension and upheld multiple times)... former Packer Jarran Reed got 6 games (DV allegations, never charged nor arrested), Big Ben got 6 games (reduced to 4, no charges), etc...
Probably more worrisome however is the possibility of landing on the Commissioner's Exempt List. It's basically paid suspension; Jacobs would still get paid but would be ineligible to play or practice while the league investigates. And that can more or less be indefinite.
The league CBA also stipulates that players agree that the commissioner has the authority to impose discipline for any "conduct detrimental to the integrity of, or public confidence in, the game of professional football". In other words, the players' union agrees that the commissioner can punish you if you make the league look bad, and that's pretty much it. Doesn't need charges...so "credible evidence" is the operative bit there, but for the league that's a pretty low bar to clear. Even if the local DA decides there's not enough evidence to bring charges, if the league feels there's evidence that you did anything that reflects poorly on the league (as above), that's clearing their (and the NFLPA's) standard. It's not innocent until proven guilty or beyond a reasonable doubt or anything like that.
The key distinction though is that IF a player were to try and sue the league, the courts DO NOT care if the player was actually guilty or not of what he was originally accused of. All the courts will rule on is whether or not the league followed its own arbitration and appeal process as the CBA outlines it. If the league follows the CBA discipline process it doesn't matter if Jacobs did it or not. Take the examples of Ezekiel Elliott (as mentioned) or even Tom Brady in Deflategate. Both of them tried to file suits against the league...they felt their cases were not handled properly and the result suspensions were unfair, not following the proper processes/channels/etc.... and they both lost. The precedent set by the courts basically says they are just there to ensure the CBA is adhered to.
Anyways the long and short of it is that yes, Jacobs and his camp certainly could file suit, and they would perhaps be able to delay a suspension while the matter was being adjudicated, but at the end of the day they would almost certainly lose and his suspension would stand. On the plus side though the league has been pretty much silent on the matter so I dunno, maybe that's a good sign
