I know this situation extremely well, so please consider these points:
Mr. Flynn is a fine Libertarian, but with a specific and sophisticated viewpoint on immigration that is shaped by his career as an immigration lawyer. He wants to use this campaign to expound on that viewpoint. I disagree with him that this is the best way to do so, but I acknowledge that it is his right to do so.
Meanwhile the Libertarian Party of Texas is required by law to accept all candidates who file for office as long as they meet the age and residency requirements. This is not optional. If they fail to accept his filing they will certainly be sued as Mr. Flynn doesn't even need to hire a lawyer to do so.
However the Libertarian Party has a great thing written into their rules and that is that convention delegates can vote for "None of the Above" in any race. A candidate who does not defeat "None of the Above" is not given a ballot spot. This actually occurs from time to time and, in point of fact, this very thing happened in 2006 in this exact race with this exact candidate!
Mr. Flynn did not get the nomination in 2006 and he will likely not get it in 2008. (If he does get it, it will be because many Libertarians decided to vote in the Republican primary making them ineligible to vote in the Libertarian convention and leaving just a handful of people to decide the fate of Mr. Flynn's candidacy.)
Thank you for your kind attention to these facts.