Many of the perpetrators of recent terrorist attacks in France had criminal records and became radicalized in prison by learning terrorist skills. Since they have not committed new crimes, they cannot be re-incarcerated despite the likelihood they will seek new targets. To address this, the document proposes having previously convicted terrorists and those who traveled to Syria/Iraq wear GPS-enabled electronic ankle monitors to track their locations. Additional measures like prohibiting meetings between offenders and only allowing police-monitored cell phones could help prevent radicalized individuals from coordinating further attacks without excessively restricting civil liberties.

1. Many of the perpetrators of this horrendous attack on France are
terrorists with a previous incarceration records. And it seems
that that in jail many would-be-terrorists get converted to active
terrorists, learn the skills to carry out the kind of attacks done in
Paris and become part of terror networks.. It is said that since
these ex-prisoners have not committed a subsequent offence,
they cannot be incarcerated again. Preventative detention, of
course, is not allowed or desirable in Western democracies even
though, like other habitual criminals, a previously incarcerated
terrorist is likely to look for new targets, very few terrorists are
known to "change their stripes". And yet, as the news constantly
reminds us, there are never enough police physically to monitor
these ex-offenders likely to become terrorists again.
There is, however a relatively easy answer to this conundrum.
The EU should, in a coordinated fashion, require that all
previously convicted terrorists and all would-be-terrorists who
traveled to Iraq and Syria wear home arrest electronic ankle
monitors. This would allow such individuals to be tracked in an
undefeatable, inexpensive, proven and accurate basis. Since the
monitors have GPS capability, geographic rules could be sent.
For example, the worst offenders could be required to stay at
home. There could, in addition, be an easily-enforced rule any
that two offenders, wearers of the monitors, could not meet.
An additional safeguard would be to require these previous
offenders to have only police monitorable cell phones with each
offender being on a do-not-call list to each other. And the
offenders would be prohibited from having home computers. Of
course, frequent surprise visits by police-parole agents would be
required.

2. Thus home electronic ankle monitors and monitorable cell
phones would prevent previous offenders from meeting in
person or over the phone materially lowering the threat from the
most likely re-offenders without constraining the rights of
ordinary citizens.