Constitution

Full constitution can be read at:
taoiseach.gov.ie/... (html)
OR
www.taoiseach.gov.ie/... (pdf)

Article 15.6.1

"The right to raise and maintain military or armed forces is vested exclusively in the Oireachtas."

The dail vote in the "Name and shame" section circumvented this requirement.

Article 15.6.2

"No military or armed force, other than a military or armed force raised and maintained by the Oireachtas, shall be raised or maintained for any purpose whatsoever."
The US army is raised by the US but using Shannon to transort the troops is "maintaining" it. I'm sure a judge would interpret the verb "maintain" differently though...  This is the closest there is to "neutrality" in the Irish constitution.

Article 28.3.1
"War shall not be declared and the State shall not participate in any war save with the assent of Dáil Éireann. "
Same as 15.6.1

Article 29

1.    Ireland affirms its devotion to the ideal of peace and friendly co-operation amongst nations founded on international
justice and morality. "

2.   Ireland affirms its adherence to the principle of the pacific settlement of international disputes by international
arbitration or judicial determination.

3.    Ireland accepts the generally recognised principles of international law as its rule of conduct in its relations with
other States.