Not all Amazon ebooks have DRM, but it isn't easy to tell. Books for Tor are DRM-free for example.
If you were on Windows or a Mac, the best approach would be to download via K4PC or K4Mac, and use Calibre with 3rd party plugins to strip DRM and convert to ePub. Under Linux, it may be possible to use K4PC under Wine but the details are likely to be important, and I don't know them.
I would say that DRM laws are a creation of large media companies, who have more influence than individual consumers on governments. However, in the US it probably isn't illegal to strip DRM from ebooks you bought for personal use.