Is it legal to switch SIM cards from a tracfone to an iPhone?

I'm thinking about getting an iPhone but I only want to do tracfones paying so its cheaper, so I was wondering if I could take a tracfone SIM card and put in an iPhone and if that's legal. Thanks!

The sim card will not work. Tracfone uses special phones, not just to keep you from switching phones - but they have some special features dealing with their prepaid service that a non-TracFone will not have.

So it's not a legal issue - it's a functionality issue… Just won't work.

No. TracFone SIMs and phones are intended for and tied to TracFone. They will not work when used with other phones or carriers. Here's what wikipedia has to say:

"TracFone service is limited to TracFone-branded handsets (all TracFone handsets are pre-programmed by the manufacturer; therefore, the handset is locked including its latest GSM models). Other GSM handsets will not accept TracFone SIM cards, even if unlocked. Additionally, on most handsets, some features like USB and Bluetooth have been modified by the manufacturer to prevent direct transfer of user files."