Aggregate's rules (invariants) internal vs public constructor

[radian7]

Hello

Question:
Why sometime aggreagte's rules (invariants) have public constructor nad sometime internal ?

For example:
public constructor:
https://github.com/kgrzybek/modular-monolith-with-ddd/blob/master/src/Modules/Meetings/Domain/MeetingGroups/Rules/MeetingGroupMemberCannotBeAddedTwiceRule.cs
internal constructor:
https://github.com/kgrzybek/modular-monolith-with-ddd/blob/master/src/Modules/Meetings/Domain/MeetingGroups/Rules/MeetingCanBeOrganizedOnlyByPayedGroupRule.cs

I think, that all aggregate's rules should be intenal (encapsulation), isnt it ?

Regards