An enemy alliance decided to have a new player join near our cluster, and tagged the new player immediately. My assumption is they plan to have him upgrade to gates, and use his castle to gate in their whole alliance.

The new castle is under newbie protection, so I'm not sure how we are to deal with this new threat.

Are other players able to gate to a castle in newbie protection?

I'm assuming you can't launch a dragon on a newbie castle, same as you can't launch other attacks.

Can you cast heavy mist on a newbie castle to keep a gate jammed? (expensive and you have to watch the castle to keep it jammed...but could work...)

Does anyone have suggestions for dealing with such a threat?

He must have a gate in order to gate the units..and i dont think they can gate while in protection

jamming him, will only prevent his sight on the map for now... once hes out of protection,yes you must keep an eye on him..they can give him resourses to build the gate faster
and no you cant nuke a protected colony...!!

Once hes out of protection,conquer him at once...i am not sure if you can gate to a conquered person

to verify for kolopaper you can't gate to a conquered person so hit it asap

you can not gate to a conquered person
so conquer the person as soon as possible

my understanding was, you can gate to a conquered colony, BUT the colony had to have 24 control ticks.

are you certain you can not gate to a conquered colony, no matter the ticks??

in my specific case, it ended up being a moot point...for whatever reason he dropped protection, and allied ships were moving in manually, without a gate.

We've got a nice welcoming comittee set up to hit the same tick they land.

Good luck on that!!