In the US the only things that matter in trademark are Lanham Act matters, specifically whether there's a likelihood of confusion (ignoring for the moment active use in commerce and other infringement elements). Simply returning a competitor's ad when searching someone else's trade name isn't enough (citation needed).

You might ask whether state bar ethics rules have a different take? And the answer is yes, with results all over the place. This DDG search may be of interest: https://duckduckgo.com/?q=%22bar%22+buying+competitors+keywo...