Compound Affix Ordering Generalization

In morphology, Compound Affix Ordering Generalization is a generalization which entails that Class I affixes cannot appear outside compounds, while some Class II affixes may appear both inside and outside compounds. In other words, only Class II affixes may attach to compounds.

Examples
The English Class I negative prefix in- may not attach to compound adjectives (*in-self-sufficient), while its Class II counterpart un- may (un-self-sufficient).

Link
Utrecht Lexicon of Linguistics