>person should retain (that means "pay") an expert for the advice.
Yes, and in cases where it really isn't worth the cost for professional advice, it's probably best to just back off and not make waves. It's not always worth a hassle.
I once had someone contact me saying she had trademark rights to a phrase because of use, even though not official. She found me because my site came up under the phrase at search engines. Hers never did, so there was no way to tell. I went to her site and saw that she did use the phrase and checked out what the law said, right at the Government web site. Oh, I could have taken the domain name, made an issue of it and continued to use it (still could), but even though I "loved" the phrase, I just let it go with a very nice email to her. I kept the phrase on the page, in context, and removed what was leading my page to show up at search engines.
Some things aren't worth a fight, not worth hurting someone over, and not worth legal expense or aggravation.
Some issues have come up occasionally in the Business Issues forum here. Generally people share their experiences or give a link to a site with info. There's a line on these things that needs to be watched. Some posts have "disclaimers" on them as a footnote.
Certain things, like copyright, are clear-cut to some degree and not tremendously touchy - i.e. you own the copyright on a graphic as soon as you create it, unless you're an employee or assign it by contract - are pretty commonly known, and covered at the US Gov't site. Of course there are differences in different countries.
But something like legality with deep-linking, for example, isn't so clear-cut and is a recent issue that's coming up more and more.
Then, some things vary so much from city to city. Like in some cities you can't file small claims against someone out of the area; in Los Angeles County, you can if work was done in the county. That was a while back - who knows if it's changed. Telling someone it's a good idea to specify venue in a contract is neutral enough, but it wouldn't even be possible to get specific, or have anything be up to date for sure.