In the wake of UK retailers importing and selling Japanese- and American-origin PSP's all across Europe, Sony has begun sending out "cease and desist" notices to said retailers, alleging that sales of the imported units constitutes "trademark infringement."
"We informed trade accounts of our position on this matter in a letter sent out in April," said Sony in an official statement. "[We are] now following this through and enforcing our IP rights, where necessary. The law is clear, and the activity of parallel importing of PSP products from the US/Japan is unlawful. It should be clearly understood that under no circumstances does SCE [Sony Computer Entertainment] consent to such activities."
Sony's basis for the cease and desist letters is the "PlayStation" trademark, which the company insists that retailers are using unlawfully to sell imported PSP units. Ironically, Sony hasn't yet registered the "PSP" trademark in the UK, and the process of doing so could even delay the UK launch of the system since an IT firm has owned the acronym for quite some time.
Basically, Sony doesn't want people to import because it'll cut into the bottom line when the PSP does launch in Europe. They're not the only company to do this. Nintendo is well-known for sending out cease and desist letters prior to system launches, and has routinely cracked down on the importing to Europe of Game Boy Advance and GameCube games from Japan and the US.