disabled is actually intended to prevent an element from being operated. However, if a radiobutton is disabled and checked, it can be operated by activating another radiobutton that is in the same group (this is how Chrome and Firefox behave and I haven't found anything in the specification that explicitly forbids or allows this behavior).

Possible solutions:

• disabled is only allowed for radiobuttons that are not checked.
• disabled is only allowed on the radiobutton group, but not on the single radiobutton.
• disabled on a checked radiobutton leads to the fact that the entire group can no longer be operated, thus is disabled.

The same problem occurs with <option> in <select>, where <option> has the attributes selected and disabled