ya en sede de contencioso constitutional(dado el procedimiento de acceso ..
English translation: constitutional litigation
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still has the status of contentious leglislation (given the entry/access proceedings ...)
Explanation: This is just a suggestion based on what I perceive to be the intended sense of the phrase.
It is hard to tell without more context, but "jurisdiction" seems to narrow a translation because it refers to the competence of a particular authority.
"En sede de" appears to be a quite common expression in Spanish (judging from its occurrence in many internet documents), and I am surprised not to find it in either of the otherwise very good dictionaries I have consulted.
Another possibility might be "in the ambit of" -- but again only further context could really determine this.