Changed it into:
RewriteCond %{ENV:GEOIP_CONTINENT_CODE} ^EU$ [NC]
RewriteCond %{REQUEST_URI} !^/welcome.html
RewriteRule ^(.*)$ /welcome.html [L,R]
Since I had a 500 Server Error before. This doesn't give a problem for anything outside the EU. EU people now have a "Page isn't redirecting properly"...
However, I found out that I got a "Page isn't redirecting properly", because it was still redirecting. If I simply made a static page 'welcome.html', then it works like a charm.