unconstitutional
adjective /ˌʌnˌkɒnstɪˈtjuːʃənl/
  /ˌʌnˌkɑːnstɪˈtuːʃənl/
- not allowed by the constitution of a country, a political system or an organization
- The judges declared the decision unconstitutional.
 
Oxford Collocations DictionaryUnconstitutional is used with these nouns:- infringement
 - law
 - restraint
 - …