In the grammar of Standardised Irish, there is a rule against concatenation of genitives. Only the last noun in a noun phrase in the genitive is placed in the genitive case, and lenition is used on the nouns that are left uninflected. An example is hata fhear an tí, where fear remains in the nominative case, but is lenited.
However, there are numerous examples of the use of multiple successive genitives in PUL’s works. Yet his usage is not consistent on this point. An example, in PUL’s Niamh, is neart sló tíre Lochlann, where three genitives occur in succession. Elsewhere in Niamh we find a counterexample: tá sé riamh ag gabháil páirt na Lochlannach i ganfhios, where páirt is not decline in the genitive (páirte).
The only explanation I could find is in Gerald Nolan’s Studies in Modern Irish volume 1. In chapter VI he has a section on the Bracketed Construction of noun phrases. He does not say there is any “rule” that prevents concatenation of genitives, but states that two nouns (including combinations of a noun and a verbal noun) or other noun phrases may be bracketed together in such a way that inflection is resisted. This can happen whether the inflection being dropped is the genitive, vocative or dative case. However, it is not wrong either for the unity of the noun phrase not to be shown in such a way and thus for the inflection to be shown on the first noun in the phase, which is then called the Unbracketed Construction.
Examples given include:
* go raibh a dó & dá thuistiún ag (bean an tábhairne) air – this example is from PUL’s Séadna. Bean an tábhairne is viewed as a united whole, and so there is no need to use the dative case (mnaoi).
* fuair sé an sparán & cead (tarrac as) – this is also from Séadna. Tarrac as is viewed as a whole and so there is no need to reach for genitive forms such as tairricthe.
* toisc (an saibhreas go léir a bheith aige) – the noun phrase prevents the use of the genitive.
* ó, a Íosa, a (sholas na glóire síoraí) – here the noun phrase prevents the use of the vocative.
* i gcaitheamh (oiread agus aon lá amháin) – a noun phrase resists the genitive here.
* i bhfochair (gach ríogan díobh) – a noun phrase resists the genitive here.
* duairt sé le (gach bean díobh) – a noun phrase resists the dative here.
* chun (an t-éinne amháin sin do chur chun cínn) – from PUL’s Mo Sgéal Féin, the noun phrase resists the genitive.
* tímpall (an tríú huair) – the noun phrase resists the genitive.
* ag feitheamh le (clann an uilc) – the noun phrase resists the dative.
Further examples are given in Nolan’s Grammar of Modern Irish, where Bracketed Construction is also called Absolute Construction:
* ar feadh (roinnt bheag aimsire) – where roinnt remains in the nominative.
* d’éis ceiste ‘ chur air – where ceist is unbracketed.
It seems clear that non-use of the genitive in noun phrases is just an example of Bracketed Construction — and yet the explanation given in Standard Irish textbooks is confused. Note only would the Standardisers tell you that numerous passages in PUL’s works were “incorrect” — their “rule” says so – they cannot explain the impact on vocative and dative use of bracketed noun phrases. The unbracketed use hata fir an tí is perfectly good Irish–PUL has le lántoil fir an tí in his Críost Mac Dé.