Thers the law, and there's practicality. Say someone patents a carburator that gets 100 MPG on a 75 shevy pickup with a 350 v-8. Say he wants $2000 to sell you one. Say you have a mahine shop in your basement. You can build your own copy of the carburator, put it on your car, and as long as you don't SELL copies to tother people, there isn't a darn thing they can do. Yes, technically they can take you to court, and win, for patent infringement, but since you aren't selling it, the maximum damages are the PROFIT they *would* have made selling you one - and thats not enough to recover the costs of going to court. Plus most of these songs repeat chord progressions that have been used thousands of time - ask George Harrison about "He's So Fine", err, I mean, "My Sweet Lord". Not to mention the use of weasel words like, "in the style of..." or "similar to ...."
Practicaly, there is no way to stop tabulature form being created and exchanged...and in the long run, it can be argued it generates revenue for those who own the publishing rights, as it can increase the number of times cover bands play the songs in ASCAP and BMI licensed venues. Not to mention there is a "education" exception for copyright use.