Maybe not much of a help, but this is what I found:
Do previous criminal convictions imply automatically refusal of entry or expulsion?
A previous criminal conviction can be taken into account only if they are evidence of personal conduct constituting a present threat to the requirements of public policy. The authorities must base their decision on an assessment of the future conduct of the individual concerned.
Can anyone be expelled for persistent petty criminality?
In certain circumstances, persistent petty criminality may represent a threat to public policy, despite the fact that any single crime/offence, taken individually, would be insufficient to represent a sufficiently serious threat as defined above.
Source:
http://europa.eu/rapid/pressReleasesAct ... anguage=en