>I know that it could be different in Canada and in the U.S.A.
>
>Are there laws protecting by default the look & feel of an application or would I have to contact a lawyer to do it?

Appearance ("look"): if you include custom artwork in your application (e.g. as form or _screen background), that can be protected via copyright i.e. you can prevent others from creating apps that look exactly like yours (and probably ones that look "similar").

If you hold registered trademarks e.g. "Ultimax CoolApp", you could brand your UI with that, and others would be prevented from doing so.

Function ("feel"): it can be protected, but my guess is it would require that your UI be very innovative and new, AND you have a huge amount of resources (read: cash) to be able to investigate "prior art" - make sure someone hasn't already done it, and so you can defend your patent/copyright etc. A couple of recent examples of arguably successful protection of "feel" are:

- The Ribbon Bar in Microsoft Office - officially, the Office 2007 Fluent user interface
- Multitouch in Apple devices e.g. iPad, iPhone. This is currently being litigated with several major lawsuits.

All that said, IANAL, and it's probably well worth you buying an hour of the time of a good IP lawyer.