Is it possible to force computers, who are connected to the local network, to join the domain?
The "force" term is not enough precise to provide specific help.
You can use netdom from a central computer to join them to the domain remotely (providing both local admin account and a domain account with right to join computer).
Firewall on remote computer may block netdom from connecting and join it to the domain.
If you don't have local administrative privileges, you cannot make the machine become part of the domain.
Assumes you have certain administrative privileges within the domain. You can be part of the admin group, or the right to do this can be assigned granularly.
Netdom.exe can be used for this purpose: