Generating label images with ImageMagick fails

Issue

ImageMagick allows to create labels, with the label: argument.
A command example can be found at http://www.imagemagick.org/Usage/text/#label:

  convert -background lightblue -fill blue \
          -font Candice -pointsize 72 label:Anthony \
          label.gif

In RHEL7, this command fails with an error message, stating convert: not authorized, as below.

[user@host ~]$ convert -background lightblue -fill blue \
> -font /usr/share/fonts/liberation/LiberationSans-Regular.ttf -pointsize 72 label:RHEL-7 \
> label.png
convert: not authorized `RHEL-7' @ error/constitute.c/ReadImage/454.
convert: no images defined `label.png' @ error/convert.c/ConvertImageCommand/3046.
[user@host ~]$ echo $?
1
[user@host ~]$