SnapNames is a web domain name marketplace - meaning that they only deal specifically with domains that are currently owned by somebody else. They offer daily and premium auctions, private brokerage of domains, and buy-it-now listings for buying and selling domain names, including over 30 million domain names that aren't all, as you'll find on some services, exorbitant. They have over three million customers, including a significant number of small businesses, which is worth it.
A handful of domains will have restrictions on them, which means you can only purchase them if you meet certain criteria or have authorization (some examples are .gov, .edu. and .mil). But most extensions are available to everyone. In fact, most country code Top Level Domains (ccTLDs) are available for anyone to purchase, even if you don’t reside in the country in question.
In the early 21st century, the US Department of Justice (DOJ) pursued the seizure of domain names, based on the legal theory that domain names constitute property used to engage in criminal activity, and thus are subject to forfeiture. For example, in the seizure of the domain name of a gambling website, the DOJ referenced 18 U.S.C. § 981 and 18 U.S.C. § 1955(d). In 2013 the US government seized Liberty Reserve, citing 18 U.S.C. § 982(a)(1).